This invention relates to the field of xerographic development stations.
In spite of the fact that a tremendous amount of research has been performed in the field of the development of electrostatic images by the application of developer thereto, it is desirable to still further increase development efficiency. In ordinary commercial cascade development stations, a development mixture in the form of carrier and toner is cascaded through a development zone where it first contacts an upper drum portion and thereafter follows a trajectory such that often a large portion of the developer does not contact lower portions of the drum due to high centrifugal forces acting on the developer, and this tends to prevent effective development. Furthermore, in such systems, background toner on the drum is not adequately scavenged, and this can produce unattractive copies. Additionally, excessive buildup of toner is often produced on the development electrode. Thus, it is highly desirable to substantially reduce these undesirable effects to allow for a more efficient use of the available developer mixture and to produce cleaner copy. The attainment of increased development efficiency results in the production of a greater number of copies per minute for any given drum size, or conversely results in the employment of a smaller drum for a fixed rate of copy output. Additionally, because of the increased developer efficiency, the carrier will tend to become more depleted of toner. This condition causes a greater charge imbalance to exist on the carrier which in turn can enhance developer scavenging of the background areas to produce copy free from background toner. A straightforward inexpensive means for accomplishing these results is greatly desired.